Many metallic structures, such as buried pipelines and steel reinforced concrete bridges, are protected from corrosion by cathodic protection. One form of cathodic protection employs sacrificial anodes. For such systems, remaining anode life equates to remaining structural corrosion via cathodic protection, since the sacrificial anode is consumed while protecting a metallic structure. Once a sacrificial anode becomes completely depleted, it must be replaced, so that the rebar or other metal that it protects does not corrode.
The remaining life of an embedded anode is currently difficult to assess in many situations. For example, the anode may not be visible for inspection when it is embedded in concrete (such as bridge construction), or when buried under soil to protects below grade metallic structures. Analysis of anodes subsumed by concrete necessitates removal of large portions of the structure, and similarly, unearthing buried anodes is not a trivial matter.
Even exposed anodes may pose inspection problems. For example, though anodes on ship hulls are generally exposed, inspection necessitates the use of divers or surveillance while in a dry-dock condition. Additionally, even if the anode is surface mounted, the protected asset may be remotely located in a difficult to access, or dangerous environment.
As there are no presently non-destructive methods of inspecting concealed anodes, and since some surface mounted remote anodes still pose surveillance challenges, there exists a need in the art for non-destructive and remote monitoring of cathodic protection sacrificial anodes. Additionally, there exists a need in the art for methods and apparatus to track anode life and to predict when the anode will be depleted.